Resin-Based Composite and LCU-related Factors Affecting the Degree of Cure. A Literature Review: Part 2. Light Curing Units & Related Factors

Light Curing Units In parallel with developments in resin based composite technology, there have been changes in light curing units (LCU). Broadly, there are four categories of LCUs available in the market, with the two commonest used in Dentistry being quartz tungsten halogen (QTH) lamps and light emitting diode (LED) units, though now, QTH is infrequently used in most developed countries. Argon-ion lasers and Plasma-arc lamps (PALs) had many disadvantages limiting their use. Argon-ion lasers were large devices with increased cost compared to QTHs, [1] PALs had low curing efficiency, increased shrinkage and micro leakage due to fast curing, [2] increased cost, heat and power consumption and decline of lights power output over time compared to QTHs [1,3,4]. Because of their limitations, neither LCU have been in regular use in clinical dentistry and therefore will not be discussed further.